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Ecoindex, Website Carbon, Lighthouse or Grammage compared
Grammage, Ecoindex, Website Carbon and Lighthouse, what each one does
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Tools that do not ask the same question
Ecoindex and Website Carbon assess the impact of a web page, Lighthouse assesses the quality of a page, and Grammage is there to audit a site in continuous integration and then attest the result. So these tools do not all answer the same question, and they do not necessarily replace one another.
This page compares what each one describes in its public documentation, with a link to every source, and the facts listed with a source were read on 1 October 2026. When we found nothing, we write "not found in the documentation", and when we did not check the information we write "not checked", instead of assuming the feature does not exist. We give no score to the other tools, since their authors describe them better than we can.
Grammage is one of the tools compared, so we are both judge and party. That is why we stick to characteristics anyone can check on the sites we cite, and for our part the Grammage method explains in detail how Grammage measures.
The comparison table
A cell reading "not found in the documentation" means the information is missing from the pages we read, which does not prove the feature does not exist, and a "not checked" cell means information we did not verify. Prices and conditions change, so check them on each tool’s own site.
| Criterion | Grammage | Ecoindex | Website Carbon | Lighthouse |
|---|---|---|---|---|
| What is measured | GrammageOne page or the whole siteOne page or the whole site, three passes per page, on simulated mobile and desktop | EcoindexOne page, or a site from the command lineOne page at a time on ecoindex.fr, and a whole site with the command line | Website CarbonOne pageA single URL, a single page load | LighthouseOne page or a user journeyOne page per run, and user journeys (the "user flows") |
| Calculation model | GrammageWeight, requests, DOM, practices and hostingWeight, requests, DOM elements, good practices and hosting, with Sustainable Web Design v4 for carbon | EcoindexDOM, requests and weightDOM elements, requests and weight in KB, placed against about 500,000 URLs from the HTTP Archive | Website CarbonTransferred bytesTransferred bytes with Sustainable Web Design v4, and a green hosting check | LighthousePerformance and quality, no carbonPerformance, accessibility, SEO and best practices categories, with no carbon model found in the documentation |
| Displayed unit | Grammageg CO₂ eq. and a score out of 100g CO₂ eq. per view or per page, and a score from 0 to 100 | EcoindexScore out of 100 and a letter from A to GScore from 0 to 100, letter from A to G, equivalents in g CO2e and cl of water | Website Carbong CO2e per view | LighthouseScores out of 100 and millisecondsScores from 0 to 100 per category and milliseconds, with no carbon unit found in the documentation |
| CI/CD integration | GrammageYes, with thresholds and a carbon budgetYes, GitLab CI template, with thresholds and a carbon budget that fail the job | EcoindexThrough the Lighthouse CI pluginThreshold in the command line not checked, but a plugin for Lighthouse CI with GitHub Actions, GitLab CI, CircleCI and Jenkins templates | Website CarbonNot foundNot found in the documentation, which describes no command line and no public test API | LighthouseYes, with Lighthouse CIYes, with Lighthouse CI, its thresholds to meet and its budgets |
| Source code analysis | GrammageYes, down to the file and lineYes, a dedicated job reads the repository and points to the file and line | EcoindexNot found | Website CarbonNot found | LighthouseNot found |
| Verifiable proof | GrammageYes, a signed and attested measurementYes, a measurement attested by Grammage, signed, valid for 12 months, with a public attestation page | EcoindexNot claimedThe site claims neither certification nor attestation | Website CarbonNot foundNo signed attestation found | LighthouseNot found |
| Badge | GrammageYes, with a verified signatureYes, a component that checks the signature in the browser | EcoindexNot checked | Website CarbonYes, g per viewYes, it shows the g per view | LighthouseNot found |
| API | GrammageYes, free test with no accountYes, with a free test that needs no account | EcoindexYes, through RapidAPIYes, in production through RapidAPI with a key | Website CarbonCalculation only, from bytesA single public endpoint, which calculates from bytes supplied by the caller | LighthouseYes, module and PageSpeed InsightsNode module, command line, and PageSpeed Insights as Google’s web service |
| License | GrammageProprietaryProprietary, code not published | EcoindexCC BY-NC-NDMain repository under a Creative Commons BY-NC-ND license, Lighthouse plugin announced under AGPL-3.0 on npm | Website CarbonNot checked | LighthouseApache-2.0 |
| Price | GrammageFrom €0 to €84 per year excl. VAT€0 to test one page, then €60 to €84 per year excl. VAT | EcoindexFree, with a quotaFree, 10 analyses per day and per domain name | Website CarbonFree | LighthouseFree and open tool |
Ecoindex
Ecoindex is a free service run by Green IT, which rates a page from its number of DOM elements, its number of requests and its transferred weight. Its method and sources are public, and a set of tools has grown around it, with the command line and a plugin for Lighthouse.
Its main repository is under the Creative Commons BY-NC-ND license, and its Lighthouse plugin is announced under AGPL-3.0 on npm.
Its three indicators are simple to understand, which makes it handy for raising awareness in a team or with a client, and for following a page over time without installing anything.
You pick it when you want a free reference point with a rating and a letter, for a page or, with the command line, for a site.
Source, the Ecoindex method page, read on 1 October 2026.
Website Carbon
Website Carbon estimates the emissions of a page load from the bytes transferred, with the Sustainable Web Design model. It is published by Wholegrain Digital, in London, and it is free.
It gives an immediate result, with no account, and its badge goes on a site with two lines of HTML. The site states that it gives an estimate for a single page load, and that it cannot test a password-protected page or a local server. Grammage uses the same model for its carbon estimate, applied to its own measurements of the page.
You pick it to get an estimate in g of CO2e for a page in a few seconds, or to show a simple badge on a site.
Source, how Website Carbon works, read on 1 October 2026.
Lighthouse
Lighthouse is Google’s tool that examines the quality of a page with the performance, accessibility, SEO and best practices categories. Its listed categories include no carbon estimate, which is not its purpose anyway.
It is a free and open tool, maintained by Google, with very detailed audits. It plugs into CI with Lighthouse CI, which allows thresholds to meet and budgets, and failing the build of the site when they are exceeded, and it can also follow user journeys.
You pick it to track the performance, accessibility and SEO of a site, and to keep those scores under control at every code change.
Source, the Lighthouse overview, read on 1 October 2026.
What Grammage adds
Grammage takes the idea of these tools and puts it where the decision is made, that is in the delivery pipeline of the site. Here is what its documentation describes on top of that.
It plugs into CI/CD with a GitLab CI template, score thresholds and a carbon budget that fail the job when they are exceeded, as the CI/CD integration page explains.
It also analyses the code of the repository, without a browser, with a dedicated job that points to the file and line at fault, for example an image over 200 KB or a server without compression. We did not find source code analysis in the documentation of the three other tools.
Finally, a measurement can be attested by Grammage, signed, valid for 12 months and verifiable online on a public attestation page, with a badge that checks the signature in the browser. This measurement is attested by Grammage itself, so it is not a check by an independent body.
Prices are yearly and exclude taxes. Testing one page is free and needs no account, unlimited audits locally and in CI cost €60 per year excl. VAT, and the plan with the badge and CI costs €84 per year excl. VAT. You can also try the audit.
Its own documents state its limits, since it is an estimate based on a byte model and not a measurement of energy, and the origin server stays partly invisible.
Which one to choose
It depends on the question you are asking, and nothing forces you to keep only one.
| Need | Look at |
|---|---|
| A quick, free reference point on a page, with a letter | Ecoindex |
| A carbon estimate in g per view, or a simple badge to add | Website Carbon |
| Tracking the performance, accessibility and SEO of a page | Lighthouse |
| Failing a delivery when a page goes over a threshold or a carbon budget | Grammage, or Lighthouse CI for quality criteria |
| Finding in the repository the files that make pages heavier | Grammage |
| Showing a client a dated measurement that can be verified online | Grammage, remembering that the measurement is attested by ourselves |
You can also use them together, for example Lighthouse CI for the quality of each page, Ecoindex or Website Carbon for a quick reference point, and Grammage for the carbon budget and the code of the repository. The figures will not be the same from one tool to the next since the models differ, so it is better to follow the values of one tool over time. The method explains the choices of Grammage.
Sources and updates
The facts listed with a source come from the following pages, read on 1 October 2026. Prices and conditions change, so check them on each tool’s own site.
- Ecoindex, how it works
- Ecoindex, home page
- Ecoindex, command line (README)
- Ecoindex, Lighthouse plugin and Lighthouse CI (guide)
- Ecoindex, API and badge (repository)
- Ecoindex, license of the main repository
- Website Carbon, how it works
- Website Carbon, FAQ
- Website Carbon, badge
- Website Carbon, API documentation
- Sustainable Web Design, estimating digital emissions
- Lighthouse, overview (Chrome for Developers)
- Lighthouse, user flows
- Lighthouse CI (web.dev)
- Lighthouse, project repository
Last updated on 1 October 2026.
If you see a factual error, or if you publish one of these tools and its description is not accurate, write to us through the contact page and we will correct it without delay.
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